1. Field of the Invention
This invention relates to an electrophotographic photosensitive member, and a process cartridge and an electrophotographic apparatus which have the electrophotographic photosensitive member. More particularly, it relates to an electrophotographic photosensitive member having a surface layer containing a specific resin, and a process cartridge and an electrophotographic apparatus which have such electrophotographic photosensitive member.
2. Related Background Art
In recent years, electrophotographic photosensitive members having various organic photoconductive compounds are brought forth energetically. For example, U.S. Pat. No. 3,837,851 discloses a photosensitive member having a charge transport layer containing triarylpyrazoline, and U.S. Pat. No. 3,871,880 discloses a photosensitive member having a charge generation layer and a charge transport layer, the former containing a derivative of a perylene pigment.
The organic photoconductive compounds have their own different wavelength regions where they are sensitive. For example, Japanese Patent Applications Laid-open No. 61-272754 and No. 56-167759 disclose compounds having a high sensitivity at the visible region, and Japanese Patent Applications Laid-open No. 57-19576 and No. 61-228453 disclose compounds having a sensitivity up to the infrared region. Of these materials, those having a sensitivity at the infrared region are used in laser beam printers and LED printers, and the demand for them and its frequency are increasing.
Meanwhile, as a matter of course, electrophotographic photosensitive members are required to have sensitivities, electrical properties, mechanical properties and also optical properties which are suited for electrophotographic processes to be applied. In particular, since electrical and mechanical force of charging, exposure, development, transfer, cleaning and so forth is applied directly to the surfaces of electrophotographic photosensitive members repeatedly used, the photosensitive members are required to have a durability thereto.
Stated specifically, the photosensitive members are required to have a durability against deterioration caused by ozone and nitrogen oxide generated at the time of charging and against electrical and mechanical deterioration such as surface wear and scratches caused by discharging and cleaning. In particular, to improve the durability of organic photosensitive members most of which have a relatively low hardness, the lubricity of photosensitive member surfaces and the strength of resins used are given as important factors therefor.
With regard to the improvement in the lubricity, Japanese Patent Applications Laid-open No. 5-72753, No. 6-51544, No. 6-75415 and No. 6-136108 propose a method in which a siloxane chain is copolymerized on the backbone chain of polycarbonate.
However, in some cases, an attempt to improve the lubricity by straight-chain copolymerization of a conventional siloxane structure on the backbone chain of polycarbonate has resulted in a lowering of the mechanical strength inherent in polycarbonate resins, which may differ depending on its weight ratio. Wear resistance depends on the strength and lubricity of surface layers, and hence, in order to improve the durability (running performance) of photosensitive members, it is necessary to achieve both the improvement in lubricity and the prevention of resin strength from lowering.
As another problem, virgin photosensitive members have so greatly uniform surfaces that they may have a high adhesion to cleaning blades (after they have begun to be used, the photosensitive member surfaces and cleaning blades are a little improved in lubricity because the surface is scraped to become rough or the toner and wear powder become present). Accordingly, troubles such as blade turn-over and blade squeak tend to occur unless their lubricity is kept high at the service initial stage. In particular, since their surfaces have a high coefficient of friction in an environment of high humidity, this problem is remarkable not only at the initial stage but also during service.
The introduction of a straight-chain siloxane chain also makes the internal stress of a polymer film relax to bring about an improvement in solvent cracking resistance, but still tends to result in a low mechanical strength.